Question

(b) apply newton’s first law to each of the following situations. in which situations can you conclude that the object is under non - zero net force? (select all that apply.) a book sliding across the table and comes to a stop. a skydiver travels at a constant speed toward a distant star. a cd travels in a circular path around a circular track. a proton in a particle accelerator moves faster and faster. a helicopter whose combined all rest in steady space.

Explanation:

To solve this, we analyze each option using Newton’s first law (an object in motion stays in motion with constant velocity unless a net force acts on it; acceleration implies a net force):

Option A:

A book sliding across a table and coming to a stop. The book slows down (decelerates), so there’s a net force (friction) acting on it. Thus, it is not under balanced forces.

Option B:

A skydiver falling at a constant speed toward a distant star. Constant speed means zero acceleration ($a = 0$). By Newton’s second law ($F_{\text{net}} = ma$), if $a = 0$, then $F_{\text{net}} = 0$ (balanced forces, e.g., gravity and air resistance cancel). Thus, it is under balanced forces.

Option C:

A CD travels in a circular path around a circular track. Circular motion requires centripetal acceleration (direction of velocity changes), so $a
eq 0$. By $F_{\text{net}} = ma$, $F_{\text{net}}
eq 0$ (unbalanced force provides centripetal force). Thus, it is not under balanced forces.

Option D:

A proton in a particle accelerator moves faster and faster. Speeding up means positive acceleration ($a > 0$), so $F_{\text{net}} = ma
eq 0$ (unbalanced force from the accelerator). Thus, it is not under balanced forces.

Option E:

A helicopter whose (combined) all - real - in - reality force is in - reality (likely a typo, but if net force is zero or balanced). However, from the context, the only case with balanced forces is when acceleration is zero (constant velocity), which is Option B.

Answer:

B. A skydiver falling at a constant speed toward a distant star.